Production of aliphatic di-car-boxylic acids



' Patented Aug.8, 1933 PRODUCTION OF ALIPIIA'I'IO III-CAR- BOXYLIO ACIDS Walther Schrauth, Berlin-Wilmendorl, Germany, assignor, by mesne assignments, to E. I. du Pont de Nemours & 00., Wilmington, DeL, a Corporation of Delaware No Drawing. Application February 10, 1927,

serlfizlgo. 167,360, and in Germany February 8 Claims. (01. 260-112) This invention relates to the production of allphatic di-carboxylic acids. When cyclo-hexanol, cyclo-hexanone or the like compounds are oxidized under usual conditions by means of nitric,

chromic or other suitable acids, considerable amounts of decomposition products such as succinic acid, glutaric acid 810. are always formed besides adipic acid. This also applies, to an increased degree, to alkyl-substituted hydrogenated phenols.

Now I have found that the course of reaction is favored in two respects by the addition of an oxidative catalyst, for instance metallic oxids and the salts derived therefrom, such as mercuric oxid or mercuric sulfate, molybdenic oxid and, especially, vanadic oxid or ammonium vanadate. Such additions enable me to proceed with lower temperatures and with a considerably reduced quantity of oxidizing agents, and furthermore the decomposition is diminished to a minimum, whereby the yield of di-carboxylic acids (adipic acid 81c.) primarily formed is considerably increased.

The same advantages appeal-when any de- 25 sired hydroaromatic, especially alicyclic alcohols,

' such as tetrahydronaphthol or decahydronaphthol are subjected to oxidation.

My invention enablesoxidation, for instance, at 50 to 60 0., whereas without the addition of a catalyst the oxidation does not take place at all, or only to a slight degree, at this temperature, and a temperature of 90 to 95 C is required for maintaining the reaction. Owing to the higher temperature an increased decomposition takes place being observable by greater quantities of carbon-dioxide formed and an increased consumption oi nitric acid.

Of course, I may employ as starting materials the primary oxidation products of the cyclic alcohols, i. e. the respective ketones, for instance tetrahydro-naphthalene-ketone, or hydrindone 820. instead of the cyclic alcohols themselves.

Examples 1. 200 grams of cyclohexanol are slowly and dropwise added to 840 grams of nitric acid. oi 50% HNO: containing 0.4 gram of ammonium vanadate, the initial temperature of the acid being 50 C. The reacting mass is kept at 50-60" C. by intense oooling. 220-225 grams of adipic acid were obtained; from the mother liquor 50 grams of a mixture of acids were separated, mainly consist-- to 50-60" C., and after addition 0152 grams of ammonium vanadate or 5 grams of molybdenic oxid 1 kilogram of methyl-cyclohexanol is slowly run in, care being taken that thereaction temperature may not exceed C. After completing the oxidation the acid solution is evaporated 0 to about one fourth of its total volume and cooled down. The crude methyl-adipic acid separates forming fine crystals; by recrystallizing the acid from a little hot water it is obtained with a yield of 950 to 1000 grams. A further amount of 250-300 grams may be obtained from the mother liquor, after separating the catalyst, by complete evaporation.

When operating without a catalyst the total yield of acids obtained in several steps amounted to 85-105% of the hydrophenol employed, whereas with the catalyst the least yield was 120%, only 62% of the nitric acid required when operating without a catalyst being needed.

3. 228 grams of p-methyl-cyclohexanol are oxidized with 1000 grams of nitric acid of 60% HNOa to which 200 grams of water and 2.5 grams ofmercuric sulfate have beenadded. The oxidation begins at 50 C. which temperature is maintained during the introduction of the methyl-cyclohexanol. 223 grams of methyladipic acid and 50 grams of low-molecular acids were obtained.

4. In the same manner as described in the foregoing example, 245 grams of adipic acid are obtained from 200 grams of cyclohexanol. The product, after recrystallization from water, has a definite melting point of 151-152 C. and a pure white color.

In the same manner as described in Example 2, a-p-dimethyl-adipic acid is obtained by oxidizing 1,3,5-hexahydroxylenol.

5. 800 grams of decahydronaphthol are gradually introduced into 3.5 kilograms oi'a 60% nitric acid, heated to about 50 C., to which 1.5 grams of ammonium vanadate were previously added. The treatment of the oxidation products yields substantially a mixture of cisand transhexahydro-o-phenylene-diacetic acid melting at 164 C and 151 C. respectively, and hexahydroo-carboxylic phenyl propionic acid which products may be separated in any suitable way.

I claim:-

a 1; The process of producing aliphatic dicarboxylic acids comprising the oxidation of material of the group consisting of hydro-aromatic and alicyclic alcohols and their primary oxidation 1 products by an oxidizing acid in the presence of an oxidation catalyst derived from a polyvalent metal. 110

2'. The process of producing aliphatic dicarboxylic acids comprising the oxidation of material of the group consisting of hydro-aromatic and alicyclic alcohols and their primary oxidation products by an oxidizing acid in the presence of an oxidation catalyst derived from a polyvalentmetal at a temperature approximating to 3. 'Ihe process of producingaliphatic dicarboxylic acids comprising the oxidation of material oi the group consisting of hydro-aromatic and alicyclic alcohols and their primary oxidation products by an acid 01 the group consisting of concentrated nitric acid and chromic acid in the presence of a catalyst of a group consisting of mercuric oxide, mercuric sulfate, molybdenic oxide,'vanadic oxide and ammonium vanadate.

4. The process oi. producing aliphatic dicarboxylic acids comprising the oxidation of material of vthe group consisting of hydro-aromatic and alicyclic alcohols and their primary oxidation products by an oxidizing acid in the presence or a catalyst consisting of a vanadium-oxygen compound 6. process of producing aliphatic dicarboxylic acids comprising the oxidation by a strong oxidizing acid of an alicyclic alcohol in the presence of an oxidation catalyst comprising a polyvalent metal oxide capable of forming an acid.

6. The process of producing adipic acid comprising oxidizing a material of the group consisting of-cyclohexanol and cyclo-hexanone by an oxidizing acid in the presence of an oxidation catalyst comprising -a polyvalent metal oxide capable of forming an acid.

'7.The process of producing adipic acid comprising oxidizing a material of the group consisting of cyclohexanol and cycio-hexanone by an oxidizing acid in the presence of an oxidation-catalyst comprising a polyyalent metal oxide capable of forming an acid at a temperature approximating 50 to C. p

8. The process of producing aliphatic dicarboxylic acids comprising the oxidation of hydroaromatic alcohols containing six or more carbon atoms by strong oxidizing acids in the presence of an oxidation catalyst comprising a polyvalent metal oxide capable of forming an acid.

WALTI-IER SCHRAUTH. 

